Steel frames get "springy" with age?

2»

Comments

  • So a pro cyclist's arse is more sensitive than a calibrated load cell in a material science lab? :lol:
  • dennisn
    dennisn Posts: 10,601
    I don't know that being a highly skilled and strong rider, racer makes you an expert on bicycles. I have known more than a few guys who ride and race constantly, yet have all
    their work done in a shop because they don't have any real mechanical ability. Then i have meet a few people who hardly ride at all but can wrench on a bike like no one I've ever seen. Go figure.

    Dennis Noward
  • mididoctors
    mididoctors Posts: 18,948
    I have noticed the difference in a frame shortly before it cracks.. I have snapped at least 4 frames IIRC

    at least 3 at the down tube head tube join and one at the seat tube bottom bracket

    I could tell when something was up... but only very shortly before it snapped/tore apart

    those breakage points are clearly the "flex zones" exposed to repetitive stress

    wouldn't say the frame became "dead".. though a new frame does often feel better just because its a change ie mostly psychological
    "If I was a 38 year old man, I definitely wouldn't be riding a bright yellow bike with Hello Kitty disc wheels, put it that way. What we're witnessing here is the world's most high profile mid-life crisis" Afx237vi Mon Jul 20, 2009 2:43 pm
  • No, what you felt was probably the flex caused by a big crack shortly before it sheared all the way through.

    FFS, YOUNG'S MODULUS IS A MATERIAL CONSTANT!
    (yep I've got to get something to eat - I'm grumpy :oops: )
  • No, what you felt was probably the flex caused by a big crack shortly before it sheared all the way through.

    FFS, YOUNG'S MODULUS IS A MATERIAL CONSTANT!
    (yep I've got to get something to eat - I'm grumpy :oops: )

    yeah quite possibly but then i never said...etc
  • aracer
    aracer Posts: 1,649
    FFS, YOUNG'S MODULUS IS A MATERIAL CONSTANT
    Remember - physics doesn't apply to bicycles. Why should a scientist know better than somebody who spends 8 hours a day in the saddle?
  • aracer wrote:
    FFS, YOUNG'S MODULUS IS A MATERIAL CONSTANT
    Remember - physics doesn't apply to bicycles. Why should a scientist know better than somebody who spends 8 hours a day in the saddle?

    I hope you are joking. :roll: :?
  • A metal alloy (and steel is one) can change its characteristics over time. All alloys are treated in order to be pre-aged.
    However small changes cannot be ruled out completely.
    Whether these changes can occur within the lifespam of a normal bike and more importantly, whether these changes can be perceived by someone riding the bike... well, honestly I doubt.
    The same can be said about aluminium and titanium alloys, just they haven't been around long enough for anyone to claim his frame being springy.
    I would be far more concerned about the long terms stability of the epoxy resin used to make carbon composite frames. Especially the degradation due to UV light, well documented for most thermoset resins...
    Be scared, be very scared!

    If your frame is too "springy", add 5 psi to your tyre pressure, that will balance.
    left the forum March 2023
  • aracer
    aracer Posts: 1,649
    aracer wrote:
    FFS, YOUNG'S MODULUS IS A MATERIAL CONSTANT
    Remember - physics doesn't apply to bicycles. Why should a scientist know better than somebody who spends 8 hours a day in the saddle?

    I hope you are joking. :roll: :?
    You could just check my previous postings on this thread (and elsewhere) and make an educated guess :wink:
  • Sjaak
    Sjaak Posts: 99
    This is a well-known effect, known as 'metal fatigue' in the field of material sciences. When the cyclic stress rate is high and powerful enough, one speaks of 'high cycle fatigue'.






    :twisted:
  • I've noticed the difference in 'stiffness' (I know stell is the 'same' stiffness froma metallurgy point of view ) between steel TIG welded frames and lugged frames.

    Lugged frames seem to me to be a lot 'springier' and forgiving - I suspect because with TIG welding the tubes are fused together (almost impossible to repair a TIG welded steel frame) rather than with lugs the filler is acting a glue (for want of a better word).

    My Rey 520 TIG frame is much less springy than my lugged 531 one (520 and 531 are equiv tubing )
  • aracer
    aracer Posts: 1,649
    Sjaak wrote:
    This is a well-known effect, known as 'metal fatigue' in the field of material sciences. When the cyclic stress rate is high and powerful enough, one speaks of 'high cycle fatigue'.
    What exactly is the relevance of that comment (we've already mentioned above that under normal use a steel frame won't fatigue)?
  • aracer
    aracer Posts: 1,649
    Lugged frames seem to me to be a lot 'springier' and forgiving - I suspect because with TIG welding the tubes are fused together (almost impossible to repair a TIG welded steel frame) rather than with lugs the filler is acting a glue (for want of a better word).
    Yet more evidence of the fallibility of the human body as a testing tool I'd suggest.
  • aracer wrote:
    You could just check my previous postings on this thread (and elsewhere) and make an educated guess :wink:

    Oh I see. :lol:
  • JWSurrey
    JWSurrey Posts: 1,173
    The great Sheldon Brown (RIP)....
    http://www.sheldonbrown.com/frame-materials.html

    Sadly, no longer here to argue his case.
  • Yet more evidence of the fallibility of the human body as a testing tool I'd suggest.

    Did I say it was scientific ? Although I have a degree in Earth Sciences I'm afraid I don't have access to(as most people don't ), strain gauges to test these things.

    Therefore we can only go on what we percieve. Whether this is real or imagined probably depends on how much wine I've had to drink the night before...................
  • Did I say it was scientific ? Although I have a degree in Earth Sciences I'm afraid I don't have access to(as most people don't ), strain gauges to test these things.

    Therefore we can only go on what we percieve. Whether this is real or imagined probably depends on how much wine I've had to drink the night before...................

    Well from where I'm standing(sitting), people saying that they can detect changes in steel bike frame stiffness over 10 years is just about as stupid as saying "the Earth must be flat because when you put a marble on a perfectly level surface, it doesn't roll off' :roll:

    It has been said before, but for all intents and purposes, the stiffness of metals does not change over time. Now unless those steel tubes are completely rusted, IT'S ALL IN YOUR HEAD FOLKS! ... You've all been sniffin' too much frame saver compound... :lol:
  • It has been said before, but for all intents and purposes, the stiffness of metals does not change over time. Now unless those steel tubes are completely rusted, IT'S ALL IN YOUR HEAD FOLKS! ... You've all been sniffin' too much frame saver compound...

    In my original post I wasn't referring to changes over time, but rather the differences due build (TIG v lugged).

    I'm well awware that a metals properties don't change over time (unless it's rusted etc)
  • Are you absolutely sure that the tube diameters, wall thicknesses and geometry are all the same? :?
  • [/quote]Are you absolutely sure that the tube diameters, wall thicknesses and geometry are all the same?

    Oh yes indeedy !